For many reasons, it is desirable to drill a straighter hole with reduced spiraling effects along the desired drilling path and with fewer washed out sections. For instance, it has been found that tortuosity, or spiraling effects frequently produced in the wellbore during drilling, are associated with degraded bit performance, bit whirl, an increased number of drill string trips, decreased reliability of MWD (measurement while drilling) and LWD (logging while drilling) due to the vibrations generally associated therewith, increased likelihood of losing equipment in the hole, increased circulation and mud problems due to the troughs along the spiraled wellbore, increased stabilizer wear, decreased control of the direction of drilling, degraded logging tool response due to hole variations including washouts and invasion, decreased cementing reliability due to the presence of one or more elongated troughs, clearance problems for gravel packing screens, decreased ROP (rate or speed of drilling penetration), and many other problems.
When drilling wells, it is highly desirable to drill the well as quickly as possible to limit the costs. It has been estimated that doubling the present day rate of drilling would result in cost savings to the oil industry of from two hundred to six hundred million dollars per year. This estimate may be conservative.
During the drilling of a well, considerable time is lost due to the need to trip the drill string. The drill string is removed from the wellbore for any of various reasons, e.g., to replace the drill bit. Reducing the number of drill string trips, especially in deep wells where removal and replacement of the drilling string takes considerable time, would greatly reduce drilling rig daily rental costs.
While the design of drill bits has often been the chief focus in the prior art to reduce many of the problems discussed above, some efforts have been made to improve other aspects of the bottom hole assembly. The typical bottom hole assembly includes a plurality of heavy weight drill collars. The typical steel heavy weight collars are relatively inexpensive and durable. However, due to their size and construction, prior art weight collars are unbalanced to some degree and tend to introduce variations. Moreover, even if they were perfectly balanced, the heavy weight collars have a buckling point and tend to bend up to this point during the drilling process. The result of inbalanced heavy weight collars and the bending of the overall downhole assembly produces a flywheel effect with an imbalance therein that may easily cause the drill bit to whirl, vibrate, and/or lose contact with the wellbore face in the desired drilling direction.
Efforts have also been made to make heavier drilling collars. For instance, it has been attempted to increase the diameter of steel drill collars to provide increased weight adjacent the drill bit. However, this then decreases the annular space between the higher diameter steel drill collars and the wall of the bore hole. The decrease in annular space creates a significant washout of the hole due to the necessarily higher velocity mud flow through a smaller annulus, especially in uncompacted formations.
Other attempts to increase the weight of the downhole assembly include the use of high density materials such as sintered tungsten and depleted uranium. However, significant problems have been encountered in mounting the high density sintered tungsten or depleted uranium due to the brittle nature thereof which has resulted in shortened life spans for such drilling collars. In one embodiment discussed in more detail in the below-listed prior art patents, threads are cut into the brittle heavy weight material itself. These threads are apparently highly subject to failure. In another embodiment, attempts are made to limit particular types of drilling stresses applied to the high density material. In this design, a thick steel jacket is utilized to attempt to absorb torsional, bending stresses, and other stresses while permitting compressive stress to be applied to the high density material which the brittle high density material is able to withstand. However, due to the compression mounting of the brittle sintered tungsten weight section to the surrounding thick steel jacket, the torsional and bending stresses are inevitably applied to the brittle sintered tungsten. Therefore, it appears that early failure is also likely for this design. The thick steel jacket also significantly limits the volume of high density material that can be utilized. The oil and gas drilling industry has long sought and continues to seek solutions to the above problems.
The following patents describe in more detail previous attempts made in the prior art to address the above problems:
U.S. Pat. No. 4,278,138, issued Jul. 14, 1981, to Rowley et al., discloses a composite drill collar for drilling bore holes in earth formations including a structural steel outer jacket having a lower end secured to a lower coupling connectable to a drill bit and an upper end secured to an upper coupling connectable to an adjacent drill collar thereabove. An annular heavy metal core of sintered tungsten is disposed in the jacket and is held in compression therein by preloading the lower and upper couplings against the ends of the core, which places the jacket in tension, causing the jacket to contract and grip the periphery of the core. The structural steel jacket has a thick wall to carry the bending, torsion, compression, tension and impact loads encountered in the drilling operation, so that such loads are not carried through the core, which has the purpose of increasing the overall density and mass of the composite drill collar, lessening considerably the tendency for a deviated well bore to be produced.
U.S. Pat. No. 1,792,941, issued Feb. 17, 1931, to E. E. Stevenson, discloses a pump barrel comprising a jacket having internal threads formed in the ends, and a centralizing recess at the inner ends of the internal threads; an intermediate liner in the jacket which is smaller in external diameter than the internal diameter of the jacket; end liners in the ends of the jacket which engage the intermediate liner and are of smaller external diameter than the internal diameter of the jacket; centralizing shoulders formed on the end liners, and rested in the centralizing recesses for centralizing the liners; and end collars screwed into the internal threads for clamping the liners together, the collars having inner end faces perpendicular to the axis of the liners.
U.S. Pat. No. 2,126,075, issued Aug. 9, 1938, to J. C. Wright, discloses a drill collar for use in a rotary drilling string including a body to be connected in the string and having sufficient strength for the transmission of the forces to which the string is subjected, a tubular part around the body, coupling means on the upper end of the part for connecting with a washover pipe whereby the part is adapted to operate as a continuation of the washover pipe, and means removably connecting the outer part with the body.
U.S. Pat. No. 2,814,462, issued Nov. 26, 1957, to F. D. De Jarnett, discloses a drill collar for connection between upper and lower portions of a drill column, upper and lower portions extending upwardly to a rotary table and downwardly to a drill bit, respectively, the drill collar both providing weight for downward pressure on the drill bit and for minimizing the transmission of vibration and shock forces from the drill bit to the drill column, the drill collar comprising: inner tube means having a longitudinal flow passage for communication with the drill column, upper coupling means fixed to the upper end of the inner tube means and adapted for connection with the lower end of the upper portion of the drill column, lower coupling means fixed to the lower end of the inner tube means and adapted for connection with the upper end of the lower portion of the drill column, outer tubular means having an upper end also connected to the upper coupling means and having a lower end connected to the lower coupling means, the outer tubular means surrounding at least a portion of the inner tube means and being spaced a predetermined distance therefrom to form a chamber therewith, a passageway extending from the exterior into the interior of the chamber, the chamber containing a selected medium comprising at least a liquid, the liquid only partially filling the chamber, mans to provide a liquid-tight seal for the chamber including means to seal the passageway, whereby vibratory and shock forces transmitted to the coupling means will be at least in part transmitted to the medium, the turbulence of the liquid created by the flow thereof in the chamber thereby dissipating at least some of the energy of the vibratory and shock forces.
U.S. Pat. No. 2,958,512, issued Nov. 1, 1960, to H. C. Humphrey, discloses a drill collar of composite construction comprising threaded end sections and inner and outer pipe members joined thereto in concentrically spaced relationship to each other thereby defining an annular chamber therewith, the pipe members being equal to and not greater than standard size drill pipe with conventional diametral dimensions, the drill collar being adapted to be attached to a drill string having the same outer diametral dimension, each of the threaded end sections having the same outer diametral dimensions as the outer pipe member and having an axial passageway with the same inner diametral dimension as that of the inner pipe member, and a metallic material completely occupying the annular chamber and having a higher specific gravity than the pipe members and the end sections and with comparable tensile strength to provide a drill collar of substantially the same or greater weight and of lesser outer diametral dimensions in comparison with a conventional integral drill collar, the metallic material comprising an alloy of lead having a specific gravity ranging from 9.4 to 11.3.
U.S. Pat. No. 3,047,313, issued Jul. 31, 1962, to G. H. Bruce, discloses a drill collar for use in a drill string which comprises inner and outer spaced apart tubular wall members, cellular reinforcing means between and bondedly attached and secured at least to a wall members throughout the length thereof, the cellular reinforcing means forming a plurality of cells in and throughout the length and width of the space with passageways in the cellular reinforcing means into each cell, the inner of the wall members providing an unobstructed bore for passage of fluid, means attached to each end of the wall members for connecting the drill collar into a drill string, and metal weighting means having a specific gravity greater than 8.0 in and filling the cells whereby a heavy drill collar and a pendulum effect to the drill string are provided, the cellular reinforcing means being formed of a high melting point metal substantially chemically inert to and unattacked by the metal weighting means received into the cells in a liquid state.
U.S. Pat. No. 3,062,303, issued Nov. 6, 1962, to W. E. Schultz, discloses a method of changing during drilling operations the direction of a well which is inclined to the vertical, the method comprising inserting and rotatably mounting in a drill string above a drill bit an eccentrically weighted tool adapted to expand an element radially against the wall of the well, placing the element in pressure communication with the interior of the drill string, lowering the drill string and tool to substantially the bottom of the well, reciprocating the drill string from the surface with sufficient force to jar the tool causing it to turn about the drill string axis to a desired position, applying fluid pressure through the drill string to expand radially against the well wall the expandible element of the rotatably mounted tool to force the tool to one side of the well, and subsequently rotating the drill string and bit within the well to resume drilling operations.
U.S. Pat. No. 3,167,137, issued Jan. 26, 1965, to H. C. Humphrey, discloses in combination, in a drill collar of composite construction subject to rotation, end sections and inner and outer pipe members joined thereto in concentrically spaced relationship to each other thereby defining an annular chamber therewith, the drill collar being adapted to be attached to a rotatable drill pipe string having the same outer diametral dimensions, each of the end sections having the same outer diametral dimension as the outer pipe member and having a passageway in coaxial communication with and with a diameter equal to the inner diameter of the inner pipe member, a metallic material completely occupying the annular chamber and having a higher specific gravity than the pipe members and the end sections to provide a drill collar of substantially the same or greater weight and of lesser outer diametral dimension in comparison with a conventional integral drill collar, the metallic material being selected from the group consisting of lead and an alloy of lead having a specific gravity ranging from 9.4 to 11.3, and a plurality of resilient metallic members fixedly fastened to and spaced along the length of one of the pipe members within the annular chamber, the metallic members projecting equidistantly from one of the pipe member into contact with the other of the pipe members with respect to each other, the metallic members being imbedded in the metallic material to serve as anchors therefor.
U.S. Pat. No. 3,195,927, issued Jul. 20, 1965, to W. B. Kimbrell, discloses a weight pipe comprising an outer member prestressed in axial tension and having an upper end and a lower end, an inner tube prestressed in axial compression disposed in the outer member and having an upper end and a lower end, the upper end of the inner tube being press fitted with an interference fit within the upper end of the outer member forming an overload releasable joint between the upper ends, the lower end of the inner tube being press fitted within the lower end of the outer member forming a joint between the upper ends of the inner tube and outer member requiring less overload torque to cause relative motion therebetween than would be required to cause relative motion at the joint between the lower ends of the inner tube and outer member whereby the joint at the lower ends is stronger with respect to torque resistance than the press fit joint between the upper ends of the inner tube and the outer member, the outer diameter of the upper end of the inner tube at the joint with the upper end of the outer member being larger than the diameter of the lower end of the inner tube at the joint with the lower end of the outer member, means cooperatively disposed between the inner tube and outer member adjacent the upper ends thereof to transmit axial tension from the inner tube to the outer member when the overload releasable joint has released but allowing rotation of the upper end of the outer member relative to the inner tube when the overload releasable joint has released, the inner tube being separated from the outer member between the joints forming an annular chamber extending from the joint between the upper ends to the joint between the lower ends, both of the joints being rendered fluid tight, and a fluid having a density greater than 1.4 filling the chamber, the joints being constructed and arranged to maintain the tension and compression so long as the overload releasable joint is not released.
U.S. Pat. No. 3,232,638, issued Feb. 1, 1966, to M. B. Hollander, discloses a hollow drill collar comprising, in combination, a pin connection having an outward facing annular shoulder, a box connection having an inward facing annular shoulder, an outer tubular member having high tensile strength to which the pin and box connections are screwed, and an inner tubular member longer than the outer member and having high compressive strength, both tubular members being loaded within their respective yield points, the inner member being of a length greater than the axial distance between the shoulders when the pin and box connections are tightly screwed into the outer tubular member, the inner tubular member being concentrically disposed within the outer tubular member with slight radial clearance forming an annular recess between the tubular members extending substantially the axial length of the inner member prior to loading the inner member, the annular shoulders of the pin and box connections contacting and compressing the inner tubular member when the connections are screwed to the outer tubular member, the inner tubular member being loaded in compression substantially to the critical point, causing the inner tubular member to buckle and contact the inner walls of the outer member, the inner walls preventing further buckling of the inner member at the point of contact, thereby restraining the inner tubular member to stress within its yield point, the arrangement being such that the outer member is prestressed in tension within its yield points, thereby to stiffen the drill collar against radial deformation as the collar is subjected to compressive loading.
U.S. Pat. No. 3,572,771, issued Mar. 30, 1971, to Fletcher Redwine, discloses a drill-collar construction for use in rotary drilling of well. The individual collars are joined end-to-end with connectors which have greater fatigue resistance than the steel of the drill collars. The preferred metal for the connectors is titanium or a titanium-base alloy.
U.S. Pat. No. 3,706,348, issued Dec. 19, 1972, to Carey E. Murphey, Jr., discloses a system for controlling hole deviation through the use of a bit and a composite drill string comprising a heavy drill collar disposed above the bit and conventional steel collars above the heavy metal collar.
U.S. Pat. No. 3,955,835, issued May 11, 1976, to Percy L. Farrington, discloses a gas economizer which comprises a union for insertion in a gas line leading to a gas appliance with the male portion of the union provided with a plurality of spirally extending fins to cause a swirling action in the gas passing therethrough.
U.S. Pat. No. 4,760,889, issued Aug. 2, 1988, to Roy L. Dudman, discloses a drill collar having a fishing neck just behind the pin end, which has a reduced dimension compared with the box end. Hence, the tool is particularly well suited for being oriented with its pin end up in a drill string. The BSR is enhanced while the collar retains good “fishability”, and “washoverability”, characteristics.
U.S. Pat. No. 4,771,811, issued Sep. 20, 1988, to DeCell et al., discloses a substantially homogeneous heavy wall drill pipe and its method of manufacture. A cylindrical ingot is placed in a multi-hammer forging press to form the ingot into a drill pipe bar having a central protector portion and upper and lower connector sections each of larger diameter than cylindrical body sections of the drill pipe. Thereafter, the bar is straightened and upper and lower end connectors are machined. Threaded end portions are machined on the connectors and a bore is drilled through the drill pipe bar.
U.S. Pat. No. 4,776,436, issued Oct. 11, 1988, to Nenkov et al., discloses a face shock absorber with a top and a bottom adapter, between which there is mounted a housing, and in it there are disposed a spindle and active elements disposed inside a chamber enclosed by a top and a bottom disk, the housing and the spindle, and underneath the bottom disk there are disposed springs. The top adapter is embraced by a two-stepped nut with external thread, screwed up to the housing, and through the two-stepped nut pass keys. The working chamber is divided by intermediate sleeves into sections, in each of which there are disposed spherical heads, shaped in the external surface of the spindle. The active elements disposed inside the working chamber are balls. The springs are limited in their bottom end by a ring-shaped nut, and it is possible to use springs of the slotted type.
U.S. Pat. No. 4,905,776, issued Mar. 6, 1990, to Beynet et al., discloses a vibration dampening assembly, such as a dynamic balancing apparatus, which is connected to a drill bit, a downhole motor or drill string to exert a variable force to counteract vibration inducing forces. The dynamic balancing apparatus includes a support body which supports a plurality of freely movable masses so that the masses move to a position for opposing an imbalance force which rotates with, and at the same speed as, the drill bit, downhole motor or drill string.
U.S. Pat. No. 6,230,822, issued May 15, 2001, to Sullivan et al., discloses a drill bit for use in drilling operations in a wellbore, the drill bit having a bit body including a plurality of bit legs, each supporting a rolling cone cutter; a coupling member formed at an upper portion of the bit body; at least one temperature sensor for monitoring at least one temperature condition of the improved drill bit during drilling operations; and at least one temperature sensor cavity formed in the bit body and adapted for receiving, carrying, and locating the at least one temperature sensor in a particular position relative to the bit body which is empirically determined to optimize temperature sensor discrimination.
U.S. Patent Application 20020157895A1, published Oct. 31, 2002, to Dubinsky et al. discloses a plurality of heavy mass irregularities attached to an inner wall of the drill collar attenuate waves traveling through the collar. The plurality of heavy mass irregularities are spaced and sized for the maximum attenuation of acoustic pulses in a predetermined frequency range. The mass irregularities may be rings firmly coupled to the outer surface of the collar. Alternatively, the mass irregularities may be rings firmly coupled to the outer collar surface by neck pieces, extending inwardly from the inner circumference of the ring. The mass irregularities may be made of steel or tungsten. In another preferred embodiment, the mass irregularities are asymmetrically coupled to an outer collar wall for providing preferential directional attenuation.
An article from Offshore Magazine, issued August 2001, written by Chen et al., entitled “Wellbore design: How long bits improve wellbore micro-tortuosity in ERD operations,” discloses tortuosity as one of the critical factors in extended reach well operations, having two components: macro- and micro-tortuosity. The effects include high torque and drag, poor hole cleaning, drill string buckling, and loss of available drilled depth, among other negative conditions. A new drilling system using long gauge bits significantly reduces hole spiraling, one form of micro-tortuosity, which is intended by use of the drill bit design to improve many facets of the drilling operation.
The above cited prior art does not provide a durable, statically/dynamically balanced, relatively high plasticity high density material, for bottom hole assemblies to thereby dramatically improve the drilling operation by substantially solving the problems discussed hereinbefore. Consequently, there remains a need to provide an improved high density downhole assembly. Those of skill in the art will appreciate the present invention which addresses the above problems and other significant problems.